Light emitting device

ABSTRACT

A light emitting device that is capable of achieving excellent color rendering property is provided. The light emitting device contains a light emitting element having a light emission peak wavelength within a range of 430 nm or more and 470 nm or less, and a fluorescent member. The fluorescent member contains a first fluorescent material that contains an Eu-activated alkaline earth aluminate, a second fluorescent material that contains a Mn-activated fluorogermanate, a third fluorescent material that contains a Ce-activated rare earth aluminate, and a fourth fluorescent material that contains an Eu-activated silicon nitride having Al and at least one of Sr and Ca.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2016-041727, filed on Mar. 4, 2016, Japanese Patent Application No.2016-050496, filed on Mar. 15, 2016, and Japanese Patent Application No.2016-090013, filed on Apr. 28, 2016, the disclosures of which are herebyincorporated by reference in their entirety.

BACKGROUND

Technical Field

The present disclosure relates to a light emitting device.

Description of Related Art

Examples of a light emitting device emitting white light using a lightemitting diode (which may be hereinafter referred to as an “LED”)include a light emitting device having a combination of an LED emittingblue light and a fluorescent material emitting yellow light. The lightemitting device emits white light through mixing of the blue light fromthe LED and the yellow light from the fluorescent material excited bythe blue light.

The light emitting device has a large radiation intensity in the visibleregion and a large luminous efficiency, but there may be some caseswhere sufficient radiation intensities cannot be obtained in theblue-green region and the red region. Accordingly, there is room ofimprovement in a general color rendering index, which is an index of thevisibility of the color of the irradiated object (i.e., a colorrendering property).

The evaluation procedure for the color rendering property of a lightsource is determined by JIS Z8726 in such a manner that the standardtest colors (R1 to R15) having the prescribed reflectancecharacteristics are measured for colors with a test light source and thereference light source, and the color differences ΔEi (wherein irepresents an integer of from 1 to 15) are numerically calculatedtherefrom. The upper limit of the color rendering indices Ri (wherein irepresents an integer of from 1 to 15) is 100. Therefore, when the colordifference between the test light source and the reference light sourcewith a color temperature corresponding thereto is smaller, the colorrendering index is increased and is close to 100.

Japanese Unexamined Patent Publication No. 2003-535477 discloses a lightemitting device, in which the light emitting device uses an LED emittingblue light and, as two kinds of fluorescent materials emitting greenlight to yellow light, for example, a chlorosilicate fluorescentmaterial and a garnet phosphor of Y or Tb for enhancing the colorrendering property of right source. Japanese Unexamined PatentPublication No. 2008-034188 discloses a light emitting device using afluorescent material emitting red light, in addition to a fluorescentlight emitting green light to yellow light for further enhancing thecolor rendering property.

SUMMARY

Light emitting devices for illumination purposes have a wide range ofneeds including, for example, a general lighting equipment for householduse and a special lighting equipment demanded to have high colorrendering property, such as a medical lighting equipment and a museumlighting equipment. It is not easy to control the light emissionspectrum to match the reference light sources of color temperaturedemanded in these various purposes, and thereby to provide a lightsource that has extremely small color differences in the color renderingindices Ri. In particular, in the case where white mixed color light isto be provided by combining plural kinds of fluorescent materialsincluding a fluorescent material emitting yellow light to green lightand a fluorescent material emitting red light, the adjustment of thecolor components in the light emission spectra of the fluorescentmaterials becomes complicated, as compared to the case where only onekind of a fluorescent material emitting yellow light is used.Furthermore, in the case where a light emission spectrum that has anextremely small color difference in the particular color rendering indexRi with respect to the reference light source, there is a largepossibility that any of the other color differences is increased.

An object of the present invention is to provide a light emitting devicethat is capable of achieving excellent color rendering property.

A first embodiment of the present disclosure encompasses a lightemitting device containing a light emitting element having a lightemission peak wavelength within a range of 430 nm or more and 470 nm orless, and a fluorescent member, the light emitting device emitting lighthaving a correlated color temperature in a range of 3,500 K or more and4,500 K or less, the fluorescent member containing a first fluorescentmaterial that contains an Eu-activated alkaline earth aluminate, asecond fluorescent material that contains a Mn-activatedfluorogermanate, a third fluorescent material that contains aCe-activated rare earth aluminate, and a fourth fluorescent materialthat contains an Eu-activated silicon nitride having Al, and at leastone of Sr and Ca, the first fluorescent material having a content ratioin a range of 3.0% by mass or more and 55.0% by mass or less based on atotal fluorescent material amount.

A second embodiment of the present disclosure encompasses a lightemitting device containing a light emitting element having a lightemission peak wavelength within a range of 430 nm or more and 470 nm orless, and a fluorescent member, the light emitting device emitting lighthaving a correlated color temperature in a range of 4,500 K or more and5,500 K or less, the fluorescent member containing a first fluorescentmaterial that contains an Eu-activated an alkaline earth aluminate, asecond fluorescent material that contains a Mn-activatedfluorogermanate, a third fluorescent material that contains aCe-activated rare earth aluminate, and a fourth fluorescent materialthat contains an Eu-activated silicon nitride having Al, and at leastone of Sr and Ca, the first fluorescent material having a content ratioin a range of 3.5% by mass or more and 65.0% by mass or less based on atotal fluorescent material amount.

A third embodiment of the present disclosure encompasses a lightemitting device containing a light emitting element having a lightemission peak wavelength within a range of 430 nm or more and 470 nm orless, and a fluorescent member, the light emitting device emitting lighthaving a correlated color temperature in a range of 5,500 K or more and7,000 K or less, the fluorescent member containing a first fluorescentmaterial that contains an Eu-activated alkaline earth aluminate, asecond fluorescent material that contains a Mn-activatedfluorogermanate, a third fluorescent material that contains aCe-activated a rare earth aluminate, and a fourth fluorescent materialthat contains an Eu-activated silicon nitride having Al, and at leastone of Sr and Ca, the first fluorescent material having a content ratioin a range of 7.5% by mass or more and 55.0% by mass or less based on atotal fluorescent material amount.

Embodiments according to the present disclosure can provide the lightemitting device that is capable of achieving excellent color renderingproperty.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an exemplary of alight emitting device.

FIG. 2 is a graph showing the light emission spectra of light emittingdevices of Examples 1 and 2 and Comparative Examples 1 and 2.

FIG. 3 is a graph showing the light emission spectra of light emittingdevices of Examples 3 and 4 and Comparative Examples 1 and 3.

FIG. 4 is a graph showing the light emission spectra of light emittingdevices of Examples 5 to 7 and Comparative Example 4.

FIG. 5 is a graph showing the light emission spectra of light emittingdevices of Examples 8 and 9 and Comparative Example 4.

FIG. 6 is a graph showing the light emission spectra of light emittingdevices of Example 10 and Comparative Examples 4 and 5.

FIG. 7 is a graph showing the light emission spectra of light emittingdevices of Examples 11 to 13 and Comparative Example 6.

FIG. 8 is a graph showing the light emission spectra of the lightemitting devices of Examples 14 and 15 and Comparative Examples 6 and 7.

DETAILED DESCRIPTION

Embodiments for practicing the present invention will be describedbelow. The embodiments described below only exemplify light emittingdevices for practicing the technical concept of the present invention,and the scope the invention is not limited to the light emitting devicesshown below. In the specification, the relationship between the colorname and the chromaticity coordinate, the relationship between thewavelength range of light and the color name of monochromic light, andthe like are in accordance with JIS Z8110. In the case where acomposition contains plural substances that correspond to one component,the content of the component in the composition means the total amountof the plural substances contained in the composition, unless otherwiseindicated.

FIG. 1 shows a schematic cross sectional view of a light emitting device100 according to one embodiment. The light emitting device 100 containsa light emitting element 10 having a light emission peak wavelengthwithin a range of 430 nm or more and 470 nm or less, and a fluorescentmember 50. The fluorescent member 50 contains a first fluorescentmaterial 71 that contains an Eu-activated alkaline earth aluminate, asecond fluorescent material 72 that contains a Mn-activatedfluorogermanate, a third fluorescent material 73 that contains aCe-activated rare earth aluminate, and a fourth fluorescent material 74that contains an Eu-activated silicon nitride having Al and at least oneof Sr and Ca. In the following specification, the first fluorescentmaterial 71, the second fluorescent material 72, the third fluorescentmaterial 73, and the fourth fluorescent material 74 may collectively bereferred to as a fluorescent material 70.

The combination use of the light emitting element 10 having a lightemission peak wavelength within a range of 430 nm or more and 470 nm orless with the first fluorescent material 71 to the fourth fluorescentmaterial 74 enables to make the light emission spectrum of the lightemitting device close to the spectrum of the reference light source overthe relatively wide range from the short wavelength side to the longwavelength side. According to this constitution, excellent colorrendering property can be achieved.

CIE (the International Commission on Illumination) has announced theguidance for color rendering property that fluorescent lamps shouldhave, in 1986, and according to the guidance, a favorable general colorrendering index (which may be hereinafter referred to as Ra) appropriateto the place of use is 60 or more and less than 80 for factories forgeneral operations, 80 or more and less than 90 for residential houses,hotels, restaurants, shops, offices, schools, hospitals, factories forprecise operations, and the like, and 90 or more for places for clinicallaboratories requiring high color rendering property, museums, and thelike.

The light emitting device 100 has Ra of, for example, 80 or more,preferably 90 or more, and more preferably 95 or more. The upper limitof Ra is 100. The special color rendering indices are expressed byindices R9 to R15, and it is designated that R9 is for red, R10 is foryellow, R11 is for green, R12 is for blue, R13 is for the Caucasian skincolor, R14 is for the color of leaves, and R15 is for the Japanese skincolor. In particular, the index R9 is often considered in anillumination device used under an environment where edible meat ishandled, and the fidelity of hue for all the colors is often consideredin an illumination device used under an environment relating to appareland photograph. It has been said that the special color renderingindices are also preferably as high as possible, and the light emittingdevice of the embodiment has R9 to R15 of, for example, 40 or more,preferably 50 or more, and more preferably 60 or more. The upper limitsof R9 to R15 each are 100.

The light emitted by the light emitting device 100 is mixed color lightof the light emitted by the light emitting element 10 and fluorescentlight emitted by the first fluorescent material 71, the secondfluorescent material 72, the third fluorescent material 73, and thefourth fluorescent material 74, which may be light included in a rangeof x=0.00 to 0.50 and y=0.00 to 0.50 in the chromaticity coordinatedefined in CIE 1931, or may be light included in a range of x=0.25 to0.40 and y=0.25 to 0.40.

The light emitted by the light emitting device 100 may have a correlatedcolor temperature, for example, of 3,000 K or more, or 3,500 K or more.The correlated color temperature thereof may be 7,500 K or less, or7,000 K or less.

The light emitting device 100 will be described in more detail below.The light emitting device 100 emits light of a short wavelength side ofthe visible region (for example, in a range of 380 nm or more and 485 nmor less), and contains the light emitting element 10 of a galliumnitride compound semiconductor having a light emission peak wavelengthin a range of 430 nm or more and 470 nm or less, and a molded article 40carrying the light emitting element 10. The molded article 40 contains afirst lead 20 and a second lead 30 that are integrated by molding with aresin portion 42 containing a thermoplastic resin or a thermosettingresin. The molded article 40 forms a depression having a bottom surfaceand a side surface, and the bottom surface of the depression carries thelight emitting element 10. The light emitting element 10 has one pair ofan anode and a cathode, and the anode and the cathode in the pair areelectrically connected to the first lead 20 and the second lead 30respectively with wires 60. The light emitting element 10 is coveredwith the fluorescent member 50.

Fluorescent Member 50

The fluorescent member 50 contains the fluorescent material 70 thatconverts the wavelength of the light from the light emitting element 10,and a resin. The resin preferably contains a thermosetting resin, suchas an epoxy resin, a silicone resin, an epoxy-modified silicone resin,and a modified silicone resin. The fluorescent material 70 contains thefirst fluorescent material 71, the second fluorescent material 72, thethird fluorescent material 73, and the fourth fluorescent material 74.The fluorescent member 50 contains the fluorescent material 70, anddepending on necessity, may further contain other materials. Forexample, a light diffusion material may be contained to reduce thedirectionality of the light from the light emitting element forbroadening the viewing angle.

The fluorescent member 50 not only functions as the wavelengthconverting member for the light emitted from the light emitting element10 due to the fluorescent material 70 contained therein, but alsofunctions as a member protecting the light emitting element 10 from theexternal environment. In FIG. 1, the fluorescent material 70 islocalized in the fluorescent member 50. By disposing the fluorescentmaterial 70 close to the light emitting element 10 in this manner, thewavelength conversion of the light from the light emitting element 10can be efficiently performed, thereby providing a light emitting deviceexcellent in light emission efficiency. The arrangement of thefluorescent member 50 containing the florescent material 70 and thelight emitting element 10 is not limited to the arrangement, in whichthey are disposed to be close to each other, and the light emittingelement 10 and the fluorescent material 70 may be spaced in thefluorescent member 50 in consideration of the influence of heat on thefluorescent material 70. The fluorescent material 70 may be mixed in thefluorescent member 50 in a substantially uniform proportion over theentire of the fluorescent member 50, and thereby the color unevennesscan be suppressed.

Light Emitting Element 10

The light emitting element 10 has a light emission peak wavelengthwithin a range of 430 nm or more and 470 nm or less, preferably within arange of 440 nm or more and 460 nm or less, and more preferably within arange of 445 nm or more and 455 nm or less. The use of the lightemitting element 10 having a light emission peak wavelength within therange enables the effective utilization of the light emitted externallyfrom the light emitting element, so as to reduce the loss of the lightemitted from the light emitting element, and thereby a light emittingdevice having a high light emission efficiency can be provided.

The light emitting element 10 used is preferably a semiconductor lightemitting element, such as an LED. The use of a semiconductor lightemitting element as the light source can provide a light emitting devicethat has a high efficiency and a high linearity of the output withrespect to the input, and is stable with high resistance to mechanicalimpacts.

Examples of the semiconductor light emitting element used include asemiconductor light emitting element emitting blue light, or the likeusing a nitride semiconductor (for example, In_(X)Al_(Y)Ga_(1-X-Y)N,wherein X and Y satisfy 0≤X, 0≤Y, and X+Y≤1). The half value width ofthe light emission spectrum of the light emitting element 10 is notparticularly limited. The half value width may be, for example, 30 nm orless.

Fluorescent Material 70

The light emitting device 100 contains the fluorescent member 50containing the first fluorescent material 71 to the fourth fluorescentmaterial 74 as described above. The first fluorescent material 71 to thefourth fluorescent material 74 each are not limited to only onecomposition, and a combination of plural fluorescent materials differentin composition may be used for each of them. The compositional ratio ofthe first fluorescent material 71, the second fluorescent material 72,the third fluorescent material 73, and the fourth fluorescent material74 may be appropriately selected to make the characteristics of thelight emitting device, such as the light emission efficiency, the colorrendering property, and the like, within the desired ranges.

First Fluorescent Material 71

The first fluorescent material 71 is a fluorescent material thatcontains an Eu-activated alkaline earth aluminate. The first fluorescentmaterial 71 preferably has the composition shown by the followingformula (1) and is preferably a fluorescent material emitting greenlight activated by europium. According to the constitution, the lightemission characteristics of the first fluorescent material 71 describedlater can be relatively easily obtained.Sr₄Al₁₄O₂₅:Eu  (1)

The first fluorescent material 71 preferably has a maximum excitationwavelength of 270 nm or more and 470 nm or less, and more preferably 370nm or more and 460 nm or less, for exciting the fluorescent materialwithin the light emission peak wavelength of the light emitting element10 described above. The first fluorescent material 71 preferably has alight emission peak wavelength within a range of 440 nm or more and 550nm or less, and more preferably within a range of 460 nm or more and 530nm or less. When the light emission peak wavelength is in the range, theoverlaps to the light emission spectrum of the light emitting element 10and the light emission spectrum of the third fluorescent material 73described later can be reduced to make the light emission spectrum ofthe first fluorescent material 71 close to the reference light source,and thereby the color rendering property of the light emitting device100 can be enhanced. The half value width of the light emission spectrumof the first fluorescent material 71 may be, for example, 58 nm or moreand 78 nm or less, and preferably 63 nm or more and 73 nm or less. Whenthe half value width is in the range, the color purity can be enhancedto make the light emission spectrum within the green region close to thereference light source, and thereby the color rendering property of thelight emitting device 100 can be enhanced.

Content Ratio of First Fluorescent Material 71 Based on TotalFluorescent Material Amount

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the content ratio of the first fluorescent material 71 based onthe total fluorescent material amount is 3% by mass or more, preferably6% by mass or more, more preferably 15% by mass or more, and furtherpreferably 30% by mass or more. The content ratio of the firstfluorescent material 71 based on the total fluorescent material amountis 55% by mass or less, preferably 50% by mass or less, more preferably45% by mass or less, and further preferably 40% by mass or less. Whenthe content ratio is in the range, the light emission spectrum of thelight emitting device 100 emitting light having a correlated colortemperature in the range of 3,500 K or more and 4,500 K or less can bemade further close to the reference light source, and thereby the colorrendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the content ratio of the first fluorescent material 71 based onthe total fluorescent material amount is 3.5% by mass or more,preferably 6.5% by mass or more, more preferably 15.0% by mass or more,and further preferably 30.0% by mass or more. The content ratio of thefirst fluorescent material 71 based on the total fluorescent materialamount is 65.0% by mass or less, preferably 55.0% by mass or less, morepreferably 50.0% by mass or less, and further preferably 45.0% by massor less. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 emitting light having acorrelated color temperature in the range of 4,500 K or more and 5,500 Kor less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 5,500 K or more and 7,000 Kor less, the content ratio of the first fluorescent material 71 based onthe total fluorescent material amount is 7.5% by mass or more,preferably 10% by mass or more, more preferably 20% by mass or more, andfurther preferably 30% by mass or more. The content ratio of the firstfluorescent material 71 based on the total fluorescent material amountis 55% by mass or less, preferably 50% by mass or less, more preferably45% by mass or less, and further preferably 40% by mass or less. Whenthe content ratio is in the range, the light emission spectrum of thelight emitting device 100 emitting light having a correlated colortemperature in the range of 5,500 K or more and 7,000 K or less can bemade further close to the reference light source, and thereby the colorrendering property can be further enhanced.

Second Fluorescent Material 72

The second fluorescent material 72 is a fluorescent material thatcontains a Mn-activated fluorogermanate. The second fluorescent material72 preferably has the composition shown by the following formula (2) andis preferably a fluorescent material emitting dark red light activatedby manganese. The light emission peak wavelength of the fluorescentmaterial is 650 nm or more, which is relatively larger than the otherfluorescent materials emitting red light. Accordingly, the lightemission spectrum on the long wavelength side can be made close to thereference light source, and thereby the color rendering property of thelight emitting device 100 can be enhanced.(x-s)MgO.(s/2)Sc₂O₃ .yMgF₂ .uCaF₂.(1−t)GeO₂.(t/2)M₂O₃ :zMn⁴⁺  (2)

In the formula (2), x, y, z, s, t, and u satisfy 2.0≤x≤4.0, 0<y<1.5,0<z<0.05, 0≤s<0.5, 0<t<0.5, and 0≤u<1.5, and preferably satisfy y+u<1.5.In the formula (2), M represents at least one element selected from thegroup consisting of Al, Ga, and In.

In the formula (2), s and t preferably satisfy 0.05≤s≤0.3 and0.05≤t<0.3, and according to the constitution, the luminance can befurther enhanced. Furthermore, the formula (2) is preferably representedby the following formula:3.4MgO.0.1Sc₂O₃.0.5MgF₂.0.885GeO₂.0.1Ga₂O₃:0.015Mn⁴⁺According to this constitution, the second fluorescent material 72 canbe efficiently excited with light having a wavelength range containingthe light emission peak wavelength of the light emitting element.

The half value width of the light emission spectrum of the secondfluorescent material 72 is not particularly limited, and may be, forexample, 45 nm or less, and preferably 40 nm or less. When the halfvalue width is in the range, the color purity can be enhanced to makethe light emission spectrum within the red region close to the referencelight source, and thereby the color rendering property of the lightemitting device 100 can be enhanced. The light emission spectrum of thesecond fluorescent material 72 preferably has an average light emissionintensity in a range of 600 nm or more and 620 nm or less of 20% orless, and more preferably 10% or less, with respect to the maximum lightemission intensity as 100%. When the average light emission intensity inthe range is the upper limit of less, the overlap of the light emissionspectrum of the second fluorescent material 72 to the light emissionspectrum of the fourth fluorescent material 74 can be reduced, andthereby the color rendering property can be enhanced through the effectof the light emission spectrum of the fourth fluorescent material 74.

Content Ratio of Second Fluorescent Material 72 Based on TotalFluorescent Material Amount

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the content ratio of the second fluorescent material 72 basedon the total fluorescent material amount may be, for example, 25% bymass or more, preferably 28% by mass or more, and more preferably 30% bymass or more. The content ratio of the second fluorescent material 72based on the total fluorescent material amount may be, for example, 37%by mass or less, preferably 36% by mass or less, and more preferably 33%by mass or less. When the content ratio is in the range, the lightemission spectrum of the light emitting device 100 emitting light havinga correlated color temperature in a range of 3,500 K or more and 4,500 Kor less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the content ratio of the second fluorescent material 72 basedon the total fluorescent material amount may be, for example, 22% bymass or more, preferably 24% by mass or more, and more preferably 26% bymass or more. The content ratio of the second fluorescent material 72based on the total fluorescent material amount may be, for example, 32%by mass or less, preferably 31% by mass or less, and more preferably 29%by mass or less. When the content ratio is in the range, the lightemission spectrum of the light emitting device 100 emitting light havinga correlated color temperature in the range of 4,500 K or more and 5,500K or less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 5,500 K or more and 7,000 Kor less, the content ratio of the second fluorescent material 72 basedon the total fluorescent material amount may be, for example, 16% bymass or more, preferably 17% by mass or more, and more preferably 18% bymass or more. The content ratio of the second fluorescent material 72based on the total fluorescent material amount may be, for example, 24%by mass or less, preferably 20% by mass or less, and more preferably 19%by mass or less. When the content ratio is in the range, the lightemission spectrum of the light emitting device 100 emitting light havinga correlated color temperature in the range of 5,500 K or more and 7,000K or less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

Third Fluorescent Material 73

The third fluorescent material 73 is a fluorescent material thatcontains a Ce-activated rare earth aluminate. The third fluorescentmaterial 73 preferably has the composition shown by the followingformula (3) and is preferably a fluorescent material emitting yellowlight activated by cerium. According to the constitution, the lightemission characteristics of the third fluorescent material 73 describedlater can be relatively easily obtained.Y₃Al₅O₁₂:Ce  (3)

The third fluorescent material 73 preferably has a maximum excitationwavelength in a range of 220 nm or more and 490 nm or less, and morepreferably a maximum excitation wavelength in a range of 430 nm or moreand 470 nm or less, for exciting the fluorescent material within thelight emission peak wavelength of the light emitting element 10described above. The third fluorescent material 73 preferably has alight emission peak wavelength in a range of 480 nm or more and 630 nmor less, and more preferably in a range of 500 nm or more and 560 nm orless. When the light emission peak wavelength is in the range, theoverlaps to the light emission spectrum of the first fluorescentmaterial 71 and the light emission spectrum of the fourth fluorescentmaterial 74 described later can be reduced to make the light emissionspectrum of the third fluorescent material 73 close to the referencelight source, and thereby the color rendering property of the lightemitting device 100 can be enhanced. The half value width of the lightemission spectrum of the third fluorescent material 73 may be, forexample, in a range of 95 nm or more and 115 nm or less, and preferablyin a range of 100 nm or more and 110 nm or less. When the half valuewidth is in the range, the color purity can be enhanced to make thelight emission spectrum within the yellow region close to the referencelight source, and thereby the color rendering property of the lightemitting device 100 can be enhanced.

Content Ratio of Third Fluorescent Material 73 Based on TotalFluorescent Material Amount

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 18% by massor more, preferably 20% by mass or more, and more preferably 27% by massor more. The content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 59% by massor less, preferably 50% by mass or less, and more preferably 35% by massor less. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 emitting light having acorrelated color temperature in the range of 3,500 K or more and 4,500 Kor less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 20% by massor more, preferably 25% by mass or more, and more preferably 30% by massor more. The content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 60% by massor less, preferably 50% by mass or less, and more preferably 35% by massor less. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 emitting light having acorrelated color temperature in the range of 4,500 K or more and 5,500 Kor less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 5,500 K or more and 7,000 Kor less, the content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 25% by massor more, preferably 30% by mass or more, and more preferably 35% by massor more. The content ratio of the third fluorescent material 73 based onthe total fluorescent material amount may be, for example, 70% by massor less, preferably 60% by mass or less, and more preferably 50% by massor less. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 emitting light having acorrelated color temperature in the range of 5,500 K or more and 7,000 Kor less can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

Fourth Fluorescent Material 74

The fourth fluorescent material 74 is a fluorescent material thatcontains an Eu-activated silicon nitride having Al and at least one ofSr and Ca (expressed as (Sr,Ca) herein). The fourth fluorescent material74 preferably has the composition shown by the following formula (4) andis preferably a fluorescent material emitting red light activated byeuropium. According to this constitution, the light emissioncharacteristics of the fourth fluorescent material 74 described latercan be relatively easily obtained.(Sr,Ca)AlSiN₃:Eu  (4)

The fourth fluorescent material 74 contains at least one selected fromthe group consisting of Sr and Ca, and preferably contains both Sr andCa, and the content ratio of Sr in Sr and Ca is preferably 0.8% by molor more, for making the light emission peak wavelength of the fourthfluorescent material 74 within the range shown below.

The fourth fluorescent material 74 preferably has a light emission peakwavelength in a range of 620 nm or more and 650 nm or less, and morepreferably in the range of 630 nm or more and 645 nm or less. When thelight emission peak wavelength is the lower limit or more, the lightemission component between the light emission peak wavelength of thesecond fluorescent material 72 and the light emission peak wavelength ofthe fourth fluorescent material 74 may not be short, and the lightemission spectrum can be close to the reference light source. When thelight emission peak wavelength is the upper limit or less, the overlapof the light emission spectrum of the fourth fluorescent material 74 tothe light emission spectrum of the second fluorescent material 72 can bereduced, and thereby the color rendering property can be enhancedthrough the effect of the light emission spectrum of the secondfluorescent material 72. The half value width of the light emissionspectrum of the fourth fluorescent material 74 may be, for example, in arange of 80 nm or more and 100 nm or less, and preferably in a range of85 nm or more and 95 nm or less. When the half value width is in therange, the overlap of the light emission spectrum of the fourthfluorescent material 74 to the light emission spectrum of the secondfluorescent material 72 can be reduced, and thereby the color renderingproperty can be enhanced through the effect of the light emissionspectrum of the second fluorescent material 72.

Content Ratio of Fourth Fluorescent Material 74 Based on TotalFluorescent Material Amount

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the content ratio of the fourth fluorescent material 74 basedon the total fluorescent material amount may be, for example, in a rangeof 2.9% by mass or more and 3.3% by mass or less. When the content ratiois in the range, the light emission spectrum of the light emittingdevice 100 can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the content ratio of the fourth fluorescent material 74 basedon the total fluorescent material amount may be, for example, in a rangeof 2.8% by mass or more and 3.0% by mass or less. When the content ratiois in the range, the light emission spectrum of the light emittingdevice 100 can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 5,500 K or more and 7,000 Kor less, the content ratio of the fourth fluorescent material 74 basedon the total fluorescent material amount may be, for example, in a rangeof 2.4% by mass or more and 2.9% by mass or less. When the content ratiois in the range, the light emission spectrum of the light emittingdevice 100 can be made further close to the reference light source, andthereby the color rendering property can be further enhanced.

Content Ratio of First Fluorescent Material 71 Based on ThirdFluorescent Material 73

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the content ratio of the first fluorescent material 71 to thethird fluorescent material 73 is preferably in a range of 0.05 or moreand 3.00 or less, more preferably in a range of 0.50 or more and 2.00 orless, and further preferably in a range of 1.00 or more and 1.50 orless. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 can be made further close tothe reference light source, and thereby the color rendering property canbe further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the content ratio of the first fluorescent material 71 to thethird fluorescent material 73 is preferably in a range of 0.06 or moreand 4.70 or less, more preferably in a range of 0.30 or more and 2.70 orless, and further preferably in a range of 1.00 or more and 1.50 orless. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 can be made further close tothe reference light source, and thereby the color rendering property canbe further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 5,500 K or more and 7,000 Kor less, the content ratio of the first fluorescent material 71 to thethird fluorescent material 73 is preferably in a range of 0.10 or moreand 2.10 or less, more preferably in a range of 0.20 or more and 1.5 orless, and further preferably in a range of 0.40 or more and 1.00 orless. When the content ratio is in the range, the light emissionspectrum of the light emitting device 100 can be made further close tothe reference light source, and thereby the color rendering property canbe further enhanced.

Light Emission Peak Intensity Ratio of First Fluorescent Material 71Based on Light Emitting Element 10

In the light emission spectrum obtained from the light emitting device100 having the fluorescent member 50 containing the first fluorescentmaterial 71, in which the abscissa is the wavelength and the ordinate isthe light emission intensity, the light emission peak intensity ratio ofthe first fluorescent material 71 based on the light emission peakintensity of the light emitting element 10 is not particularly limited,and may be appropriately selected depending on the target correlatedcolor temperature and the desired light emission characteristics.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 3,500 K or more and 4,500 Kor less, the light emission peak intensity ratio of the firstfluorescent material 71 based on the light emitting element 10 ispreferably in a range of 0.40 or more and 0.75 or less, more preferablyin a range of 0.45 or more and 0.70 or less, and further preferably 0.50or more and 0.65 or less, with the light emission intensity of the lightemitting element 10 as 1. When the light emission intensity ratio is inthe range, the light emission spectrum of the light emitting device 100can be made further close to the reference light source, and thereby thecolor rendering property can be further enhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature in a range of 4,500 K or more and 5,500 Kor less, the light emission peak intensity ratio of the firstfluorescent material 71 based on the light emitting element 10 ispreferably in a range of 0.34 or more and 0.60 or less, more preferablyin a range of 0.35 or more and 0.55 or less, and further preferably in arange of 0.40 or more and 0.50 or less, with the light emissionintensity of the light emitting element 10 as 1. When the light emissionintensity ratio is in the range, the light emission spectrum of thelight emitting device 100 can be made further close to the referencelight source, and thereby the color rendering property can be furtherenhanced.

In the case of the light emitting device 100 emitting light having acorrelated color temperature of in a range of 5,500 K or more and 7,000K or less, the light emission peak intensity ratio of the firstfluorescent material 71 based on the light emitting element 10 ispreferably in a range of 0.25 or more and 0.42 or less, more preferablyin a range of 0.30 or more and 0.40 or less, and further preferably in arange of 0.33 or more and 0.38 or less, with the light emissionintensity of the light emitting element 10 as 1. When the light emissionintensity ratio is in the range, the light emission spectrum of thelight emitting device 100 can be made further close to the referencelight source, and thereby the color rendering property can be furtherenhanced.

The light emitting device 100 may further contain an additionalfluorescent material other than the first fluorescent material 71 to thefourth fluorescent material 74. In the case where the light emittingdevice 100 contains the additional fluorescent material, the contentthereof is not particularly limited, and may be appropriately controlledto provide the light emission characteristics according to the presentinvention.

EXAMPLES

Fluorescent Materials

The fluorescent materials shown below were prepared as the fluorescentmaterials for Examples and Comparative Examples. As the firstfluorescent material 71, a fluorescent material emitting green lighthaving a composition of Sr₄Al₁₄O₂₅:Eu having a light emission peakwavelength around 494 nm (hereinafter referred to as “SAE”) wasprepared. As the second fluorescent material 72, a fluorescent materialemitting dark red light having a composition of3.4MgO.0.1Sc₂O₃.0.5MgF₂.0.885GeO₂.0.1Ga₂O₃:0.015Mn⁴⁺ having a lightemission peak wavelength around 658 nm (hereinafter referred to as“MGF”) was prepared. As the third fluorescent material 73, a rare earthaluminum garnet fluorescent material having a composition of Y₃Al₅O₁₂:Cehaving a light emission peak wavelength around 544 nm (hereinafterreferred to as “YAG”) was prepared. As the fourth fluorescent material74, a nitride fluorescent material emitting red light having acomposition of (Sr,Ca)AlSiN₃:Eu having a light emission peak wavelengtharound 635 nm (hereinafter referred to as “SCASN”) was prepared.

Example 1

A light emitting device was produced by combining an LED emitting bluelight having a light emission peak wavelength of 450 nm with thefluorescent materials SAE, MGF, YAG, and SCASN.

The fluorescent materials having content ratios shown in Table I belowand prepared to have a correlated color temperature of approximately5,000 K were added to a silicone resin, and mixed and dispersed therein,and the mixture was deaerated, so as to provide a fluorescentmaterial-containing resin composition. The fluorescentmaterial-containing resin composition was injected and filled on thelight emitting element (i.e., the LED), and the assembly was then heatedto cure the resin composition. A light emitting device was thus producedin the aforementioned process.

Examples 2 to 4

Light emitting devices were produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios of the fluorescent materials shown in Table 1below.

The light emitting devices obtained in Examples 1 to 4 were measured forthe chromaticity coordinate of the light emission color, the correlatedcolor temperature (Tcp; K), the general color rendering index (Ra), andthe special color rendering indices (R9 to R15). In the followingdescription, the general color rendering index and the special colorrendering indices are totally and simply referred to as “color renderingindices”.

The light emission spectra of the light emitting devices of Examples 1to 4 were measured with a spectrofluorophotometer, F-4500, manufacturedby Hitachi High-Technologies Corporation. The measurements in Examplesand Comparative Examples described later were performed in the samemanner.

The results except for the color rendering indices for Examples 1 to 4are shown in Table 1 below, and the results of their color renderingindices are shown in Table 2 below. In Table 2, Rt shows the sum of thecolor rendering indices R9 to R15.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Content ratio offluorescent material (%) 6.9 17.5 35.7 53.8 First fluorescent material/total fluorescent material amount Content ratio of fluorescent material(%) 31.4 30.1 28.6 23.2 Second fluorescent material/ total fluorescentmaterial amount Content ratio of fluorescent material (%) 58.9 49.4 32.920.1 Third fluorescent material/ total fluorescent material amountContent ratio of fluorescent material (%) 2.8 3.0 2.8 3.0 Fourthfluorescent material/ total fluorescent material amount Content ratio offluorescent materials 0.12 0.35 1.08 2.68 First fluorescent material/third fluorescent material Light emission peak intensity ratio 0.34 0.360.47 0.56 First fluorescent material/ light emitting device Chromaticityx 0.348 0.345 0.343 0.348 coordinate y 0.354 0.35 0.354 0.354 Correlatedcolor temperature (K) 4874 4962 5084 4893

TABLE 2 Example 1 Example 2 Example 3 Example 4 Ra 90.1 93.4 97.4 90.2R1 89.9 93.9 97.7 88.8 R2 92.2 95.4 99.0 91.1 R3 91.0 93.3 98.5 94.7 R489.6 93.1 97.7 90.4 R5 88.4 92.3 96.7 89.9 R6 85.8 89.8 95.8 89.4 R795.5 96.5 97.2 91.0 R8 88.5 92.8 96.9 86.8 R9 65.6 80.7 95.8 66.5 R1078.2 87.0 98.5 80.2 R11 87.0 92.2 98.3 89.1 R12 59.1 65.1 75.1 74.1 R1390.0 94.7 98.6 88.5 R14 94.5 96.1 98.9 96.7 R15 89.4 94.3 95.7 86.2 Rt564 610 661 581

Comparative Example 1

A light emitting device was produced in the same manner as in Example 1except that SAE was not used, but a combination of MGF, YAG, and SCASNwas used. The content ratios of the fluorescent materials are shown inTable 3 below.

Comparative Examples 2 and 3

Light emitting devices were produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios shown in Table 3 below.

For the light emitting devices obtained in Comparative Examples 1 to 3,the results except for the color rendering indices are shown in Table 3below, and the results of the color rendering indices are shown in Table4 below.

TABLE 3 Comparative Comparative Comparative Example 1 Example 2 Example3 Content ratio of fluorescent — 3.4 67.0 material (%) First fluorescentmaterial/ total fluorescent material amount Content ratio of fluorescent33.2 32.2 16.2 material (%) Second fluorescent material/ totalfluorescent material amount Content ratio of fluorescent 64.1 61.6 13.9material (%) Third fluorescent material/ total fluorescent materialamount Content ratio of fluorescent 2.7 2.7 2.9 material (%) Fourthfluorescent material/ total fluorescent material amount Content ratio of— 0.05 4.8 fluorescent materials First fluorescent material/ thirdfluorescent material Light emission peak — 0.33 0.66 intensity ratioFirst fluorescent material/ light emitting device Chromaticity x 0.350.349 0.347 coordinate y 0.355 0.355 0.355 Correlated color 4818 48644918 temperature (K)

TABLE 4 Comparative Comparative Comparative Example 1 Example 2 Example3 Ra 87.9 88.4 83.7 R1 87.6 87.9 81.7 R2 90.0 90.6 85.2 R3 88.7 89.789.1 R4 87.5 87.9 83.6 R5 86.1 86.5 83.1 R6 82.9 83.7 81.5 R7 93.9 94.486.3 R8 86.5 86.5 79.1 R9 61.0 61.2 44.3 R10 74.0 75.5 65.7 R11 84.985.5 81.2 R12 56.9 57.3 71.5 R13 87.9 88.5 81.0 R14 93.5 94.1 93.6 R1587.8 87.9 79.0 Rt 546 550 516

As can be observed in Tables 1 and 2, Examples 1 to 4 each have largerRt than Comparative Examples 1 to 3. By controlling the amount of SAE,light emitting devices having high color rendering property may thus beprovided.

As can be observed in Table 4, Comparative Examples 1 to 3 each hassmaller Rt than the Examples, and poor color rendering property of thelight emitting device is obtained.

As shown in Table 1, Examples 1 to 4 each has a correlated colortemperature in a range of 4,500 K or more and 5,500 K or less. Examples2, 3, and 4 each has a content ratio of SAE based on the totalfluorescent material amount in a range of 7.0% by mass or more and 55.0%by mass or less, a content ratio of MGF based on the total fluorescentmaterial amount in a range of 22.0% by mass or more and 31.0% by mass orless, a content ratio of YAG based on the total fluorescent materialamount in a range of 20.0% by mass or more and 55.0% by mass or less, acontent ratio of SCASN based on the total fluorescent material amount ina range of 2.8% by mass or more and 3.0% by mass or less, and a contentratio of the first fluorescent material 71 (SAE) based on the thirdfluorescent material 73 (YAG) in a range of 0.30 or more and 2.70 orless. According to the content ratios, the light emission spectra of thelight emitting devices can be made close to the reference light source.Examples 2, 3, and 4 each has a general color rendering index Ra of 90or more, special color rendering indices R9, R10, R11, R12, R13, R14,and R15 each of 60 or more, and Rt of 570 or more. It is understood fromthese values that particularly excellent color rendering property isobtained.

FIG. 2 shows the light emission spectra of the light emitting devices ofExamples 1 and 2 and Comparative Examples 1 and 2, and FIG. 3 shows thelight emission spectra of the light emitting devices of Examples 3 and 4and Comparative Examples 1 and 3, the light emission spectra beingnormalized based on the light emission intensity at 530 nm. The lightemission spectra in FIGS. 2 and 3 each show the relative light emissionintensity with respect to the wavelength. The spectrum of the referencelight source at 5,000 K is also shown in the figures. As shown in Table1, Examples 2, 3, and 4 each has a light emission peak intensity ratioof the first fluorescent material 71 to the light emitting element 10 ina range of 0.35 or more and 0.60 or less. As shown in Table 2, Examples2, 3, and 4 each has a general color rendering index Ra of 90 or more,special color rendering indices R9, R10, R11, R12, R13, R14, and R15each of 60 or more, and Rt of 570 or more. It is understood from thesevalues that particularly excellent color rendering property is obtained.

Examples 5 to 10

Light emitting devices were produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios shown in Table 5 below, and the correlated colortemperature was controlled to around 4,000 K.

For the light emitting devices obtained in Examples 5 to 10, the resultsexcept for the color rendering indices are shown in Table 5 below, andthe results of the color rendering indices are shown in Table 6 below.

TABLE 5 Example Example Example Example Example Example 5 6 7 8 9 10Content ratio of fluorescent material (%) 3.2 6.4 15.9 35.9 43.1 50.7First fluorescent material/ total fluorescent material amount Contentratio of fluorescent material (%) 36.4 35.9 36.4 31.0 28.2 27.6 Secondfluorescent material/ total fluorescent material amount Content ratio offluorescent material (%) 57.6 54.8 44.9 30.1 25.6 18.5 Third fluorescentmaterial/ total fluorescent material amount Content ratio of fluorescentmaterial (%) 2.9 2.9 2.9 3.0 3.2 3.2 Fourth fluorescent material/ totalfluorescent material amount Content ratio of fluorescent materials 0.060.12 0.35 1.19 1.69 2.7 First fluorescent material/ third fluorescentmaterial Light emission peak intensity ratio 0.41 0.43 0.55 0.61 0.580.67 First fluorescent material/ light emitting device Chromaticity x0.381 0.38 0.388 0.382 0.376 0.384 coordinate y 0.381 0.382 0.396 0.3840.371 0.374 Correlated color temperature (K) 4002 4038 3922 4005 40613862

TABLE 6 Exam- Exam- Exam- Exam- Exam- Exam- ple 5 ple 6 ple 7 ple 8 ple9 ple 10 Ra 88.8 89.4 90.2 97.3 94.0 88.9 R1 87.9 88.5 88.8 98.5 92.986.9 R2 91.0 91.5 91.8 98.9 94.5 89.8 R3 91.2 92.1 93.7 99.0 97.7 94.1R4 88.1 88.7 89.3 96.1 94.3 88.9 R5 86.5 87.1 87.4 96.7 93.2 87.0 R685.1 86.0 87.4 97.3 92.4 85.7 R7 94.8 95.4 96.6 96.0 94.7 92.3 R8 85.986.6 86.8 96.0 92.6 86.4 R9 62.1 63.8 64.0 96.8 82.6 66.1 R10 76.9 78.880.2 98.1 88.4 77.1 R11 85.5 86.5 87.8 99.0 92.6 85.0 R12 60.9 61.6 62.574.7 77.2 75.6 R13 88.3 89.1 89.1 98.6 92.7 86.6 R14 94.8 95.4 96.3 98.898.5 96.7 R15 87.4 87.7 86.5 95.5 91.4 85.6 Rt 556 563 566 661 623 573

Comparative Example 4

A light emitting device was produced in the same manner as in Example 1except that SAE was not used, but a combination of MGF, YAG, and SCASNwas used, and the correlated color temperature was controlled to around4,000 K. The content ratios of the fluorescent materials are shown inTable 7 below.

Comparative Example 5

A light emitting device was produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios shown in Table 7 below.

For the light emitting devices obtained in Comparative Examples 4 and 5,the results except for the color rendering indices are shown in Table 7below, and the results of the color rendering indices are shown in Table8 below.

TABLE 7 Comparative Compar ative Example 4 Example 5 Content ratio offluorescent material (%) — 63.0 First fluorescent material/ totalfluorescent material amount Content ratio of fluorescent material (%)37.7 21.3 Second fluorescent material/ total fluorescent material amountContent ratio of fluorescent material (%) 59.5 13.0 Third fluorescentmaterial/ total fluorescent material amount Content ratio of fluorescentmaterial (%) 2.9 2.8 Fourth fluorescent material/ total fluorescentmaterial amount Content ratio of fluorescent materials — 4.8 Firstfluorescent material/ third fluorescent material Light emission peakintensity ratio — 0.95 First fluorescent material/ light emitting deviceChromaticity x 0.381 0.391 coordinate y 0.381 0.387 Correlated colortemperature (K) 4008 3783

TABLE 8 Comparative Comparative Example 4 Example 5 Ra 87.9 84.0 R1 87.082.5 R2 90.1 86.3 R3 90.5 89.8 R4 87.3 82.9 R5 85.6 82.3 R6 83.9 80.1 R794.4 87.5 R8 85.1 80.9 R9 59.8 55.8 R10 75.1 67.7 R11 84.4 78.4 R12 59.471.8 R13 87.4 82.0 R14 94.4 94.3 R15 86.4 82.4 Rt 547 532

As can be observed in Tables 5 and 6, Examples 5 to 10 each has largerRt than Comparative Examples 4 and 5. By controlling the amount of SAE,light emitting devices having high color rendering property may thus beprovided.

As can be observed in Table 8, Comparative Examples 4 and 5 each hassmaller Rt than the Examples, and poor color rendering property of thelight emitting device is obtained.

As shown in Table 5, Examples 5 to 10 each has a correlated colortemperature in a range of 3,500 K or more and 4,500 K or less. Examples5 to 10 each has a content ratio of SAE based on the total fluorescentmaterial amount in a range of 3.0% by mass or more and 55.0% by mass orless, a content ratio of MGF based on the total fluorescent materialamount in a range of 25.0% by mass or more and 37.0% by mass or less, acontent ratio of YAG based on the total fluorescent material amount in arange of 18.0% by mass or more and 59.0% by mass or less, a contentratio of SCASN based on the total fluorescent material amount in a rangeof 2.9% by mass or more and 3.3% by mass or less, and a content ratio ofthe first fluorescent material 71 (SAE) based on the third fluorescentmaterial 73 (YAG) in a range of 0.05 or more and 3.00 or less. InExamples 5 to 10, according to the content ratios, the light emissionspectrum of the light emitting device can be made close to the referencelight source. Examples 5 to 10 each has special color rendering indicesR9, R10, R11, R12, R13, R14, and R15 each of 60 or more, and Rt of 555or more. It is understood from these values that particularly excellentcolor rendering property is obtained.

Examples 8 and 9 each has a content ratio of SAE based on the totalfluorescent material amount in a range of 16.5% by mass or more and50.0% by mass or less, a content ratio of MGF based on the totalfluorescent material amount in a range of 28.0% by mass or more and33.0% by mass or less, a content ratio of YAG based on the totalfluorescent material amount in a range of 20.0% by mass or more and35.0% by mass or less, a content ratio of SCASN based on the totalfluorescent material amount in a range of 3.0% by mass or more and 3.2%by mass or less, and a content ratio of the first fluorescent material71 (SAE) based on the third fluorescent material 73 (YAG) in a range of0.40 or more and 2.60 or less. Examples 8 and 9 each has a general colorrendering index Ra of 90 or more, special color rendering indices R9,R10, R11, R12, R13, R14, and R15 each of 60 or more, and Rt of 600 ormore. It is understood from these values that particularly excellentcolor rendering property is obtained.

FIG. 4 shows the light emission spectra of the light emitting devices ofComparative Example 4 and Examples 5 to 7, FIG. 5 shows the lightemission spectra of the light emitting devices of Comparative Example 4and Examples 8 and 9, and FIG. 6 shows the light emission spectra of thelight emitting devices of Comparative Examples 4 and 5 and Example 10,the light emission spectra being normalized based on the light emissionintensity at 530 nm. The light emission spectra in FIGS. 4 to 6 eachshows the relative light emission intensity with respect to thewavelength. The spectrum of the reference light source at 4,000 K isalso shown in the figures. As shown in Table 5, Examples 5 to 10 eachhas a light emission peak intensity ratio of the first fluorescentmaterial 71 to the light emitting element 10 in a range of 0.40 or moreand 0.75 or less. As shown in Table 6, Examples 5 to 10 each has Rt of555 or more. It is understood from these values that particularlyexcellent color rendering property is obtained. As shown in Table 5,Example 8 has a light emission peak intensity ratio of the firstfluorescent material 71 to the light emitting element 10 in a range of0.60 or more and 0.65 or less. As shown in Table 6, Example 8 has Rt of660 or more. It is understood from these values that particularlyexcellent color rendering property is obtained.

Examples 11 to 15

Light emitting devices were produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios shown in Table 9 below, and the correlated colortemperature was controlled to around 6,500 K.

For the light emitting devices obtained in Examples 11 to 15, theresults except for the color rendering indices are shown in Table 9below, and the results of the color rendering indices are shown in Table10 below.

TABLE 9 Example Example Example Example Example 11 12 13 14 15 Contentratio of fluorescent material (%) 7.7 11.5 20.2 36.6 50.0 Firstfluorescent material/ total fluorescent material amount Content ratio offluorescent material (%) 23.0 23.1 19.2 18.8 16.7 Second fluorescentmaterial/ total fluorescent material amount Content ratio of fluorescentmaterial (%) 66.8 62.9 58.0 42.0 30.5 Third fluorescent material/ totalfluorescent material amount Content ratio of fluorescent material (%)2.5 2.5 2.6 2.7 2.8 Fourth fluorescent material/ total fluorescentmaterial amount Content ratio of fluorescent materials 0.12 0.18 0.350.87 1.64 First fluorescent material/ third fluorescent material Lightemission peak intensity ratio First fluorescent material/ 0.28 0.27 0.320.36 0.4 light emitting device Chromaticity x 0.32 0.308 0.321 0.3130.318 coordinate y 0.325 0.314 0.33 0.324 0.326 Correlated colortemperature (K) 6125 6927 6057 6523 6217

TABLE 10 Example Example Example 11 Example 12 Example 13 14 15 Ra 90.592.3 93.4 96.7 93.4 R1 91.7 93.5 94.2 96.7 91.1 R2 92.5 93.7 95.2 98.793.7 R3 88.5 89.2 92.5 96.3 98.4 R4 91.3 93.7 94.1 97.8 93.7 R5 90.491.7 92.7 95.7 92.3 R6 85.2 86.3 89.2 93.4 92.2 R7 94.4 95.8 96.2 97.794.6 R8 91.0 94.1 92.9 97.3 91.2 R9 73.6 81.8 79.7 96.9 74.7 R10 79.382.3 86.6 97.3 87.6 R11 89.9 92.7 93.6 97.7 92.1 R12 61.0 61.3 65.5 69.573.8 R13 92.2 94.4 95.2 98.3 91.2 R14 93.4 93.9 95.8 97.8 98.4 R15 93.795.5 94.9 94.7 88.1 Rt 583 602 611 652 606

Comparative Example 6

A light emitting device was produced in the same manner as in Example 1except that SAE was not used, but a combination of MGF, YAG, and SCASNwas used, and the correlated color temperature was controlled to around6,000 K. The content ratios of the fluorescent materials are shown inTable 11 below.

Comparative Example 7

A light emitting device was produced in the same manner as in Example 1except that the amounts of the fluorescent materials were changed tomake the content ratios shown in Table 11 below.

For the light emitting devices obtained in Comparative Examples 6 and 7,the results except for the color rendering indices are shown in Table 11below, and the results of the color rendering indices are shown in Table12 below.

TABLE 11 Comparative Com parative Example 6 Example 7 Content ratio offluorescent material (%) — 59.5 First fluorescent material/ totalfluorescent material amount Content ratio of fluorescent material (%)24.7 15.0 Second fluorescent material/ total fluorescent material amountContent ratio of fluorescent material (%) 73.0 22.5 Third fluorescentmaterial/ total fluorescent material amount Content ratio of fluorescentmaterial (%) 2.3 3.0 Fourth fluorescent material/ total fluorescentmaterial amount Content ratio of fluorescent materials — 2.6 Firstfluorescent material/ third fluorescent material Light emission peakintensity ratio — 0.44 First fluorescent material/ light emitting deviceChromaticity x 0.32 0.316 coordinate y 0.326 0.322 Correlated colortemperature (K) 6091 6350

TABLE 12 Comparative Comparative Example 6 Example 7 Ra 88.2 87.6 R189.1 83.7 R2 90.2 88.2 R3 86.7 94.7 R4 89.0 87.6 R5 87.9 86.0 R6 82.586.5 R7 92.7 91.4 R8 87.5 82.9 R9 63.2 49.1 R10 73.7 74.3 R11 87.2 84.3R12 58.6 74.5 R13 89.4 83.8 R14 92.4 96.3 R15 90.7 79.8 Rt 555 542

As can be observed in Tables 9 and 10, Examples 11 to 15 each has largerRt than Comparative Examples 6 and 7. By controlling the amount of SAE,light emitting devices having high color rendering property may thus beprovided.

As can be observed in Table 12, Comparative Examples 6 and 7 each hassmaller Rt than the Examples, and poor color rendering property of thelight emitting device was obtained.

As shown in Table 9, Examples 11 to 15 each has a correlated colortemperature in a range of 5,500 K or more and 7,000 K or less. As shownin Table 9, Examples 11 to 15 each has a content ratio of SAE based onthe total fluorescent material amount in a range of 7.5% by mass or moreand 55.0% by mass or less, a content ratio of MGF based on the totalfluorescent material amount in a range of 16.0% by mass or more and24.0% by mass or less, a content ratio of YAG based on the totalfluorescent material amount in a range of 25.0% by mass or more and70.0% by mass or less, a content ratio of SCASN based on the totalfluorescent material amount in a range of 2.4% by mass or more and 2.9%by mass or less, and a content ratio of the first fluorescent material71 (SAE) based on the third fluorescent material 73 (YAG) in a range of0.10 or more and 2.10 or less. According to the content ratios, thelight emission spectrum of the light emitting device can be made closeto the reference light source. As shown in Table 10, Examples 11 to 15each has a general color rendering index Ra of 90 or more, special colorrendering indices R9, R10, R11, R12, R13, R14, and R15 each of 60 ormore, and Rt of 580 or more. It is understood from these values thatparticularly excellent color rendering property is obtained.

As shown in Table 9, Examples 13 and 14 each has a content ratio of SAEbased on the total fluorescent material amount in a range of 15.0% bymass or more and 40.0% by mass or less, a content ratio of MGF based onthe total fluorescent material amount in a range of 18.0% by mass ormore and 20.0% by mass or less, a content ratio of YAG based on thetotal fluorescent material amount in a range of 35.0% by mass or moreand 60.0% by mass or less, a content ratio of SCASN based on the totalfluorescent material amount in a range of 2.6% by mass or more and 2.7%by mass or less, and a content ratio of the first fluorescent material71 (SAE) based on the third fluorescent material 73 (YAG) in a range of0.30 or more and 1.00 or less. As shown in Table 10, Examples 13 and 14each has Rt of 610 or more. It is understood from these values thatparticularly excellent color rendering property is obtained.

FIG. 7 shows the light emission spectra of the light emitting devices ofComparative Example 6 and Examples 11 to 13, and FIG. 8 shows the lightemission spectra of the light emitting devices of Comparative Examples 6and 7 and Examples 14 and 15, in each which the light emission spectraare normalized based on the light emission intensity at 530 nm. Thelight emission spectra in FIGS. 7 and 8 each show the relative lightemission intensity with respect to the wavelength. The spectrum of thereference light source at 6,500 K is also shown in the figures. As shownin Table 9, Examples 11 to 15 each has a light emission peak intensityratio of the first fluorescent material 71 to the light emitting element10 in a range of 0.25 or more and 0.42 or less. As shown in Table 10,Examples 11 to 15 each has Rt of 580 or more. It is understood fromthese values that particularly excellent color rendering property isobtained. As shown in Table 9, Examples 13 and 14 each has a lightemission peak intensity ratio of the first fluorescent material 71 tothe light emitting element 10 in a range of 0.30 or more and 0.38 orless. As shown in Table 10, Examples 13 and 14 each has Rt of 610 ormore. It is understood from these values that particularly excellentcolor rendering property is obtained.

The light emitting device of the present disclosure can be applied to anillumination device, an LED display device, a flashlight for a camera,and the like, having excellent light emission characteristics using ablue light emitting diode or an ultraviolet light emitting diode as anexcitation light source. The light emitting device of the presentdisclosure can be applied particularly favorably to an illuminationdevice and a light source that are demanded to achieve high colorrendering property.

Although the present disclosure has been described with reference toseveral exemplary embodiments, it shall be understood that the wordsthat have been used are words of description and illustration, ratherthan words of limitation. Changes may be made within the purview of theappended claims, as presently stated and as amended, without departingfrom the scope and spirit of the disclosure in its aspects. Although thedisclosure has been described with reference to particular examples,means, and embodiments, the disclosure may be not intended to be limitedto the particulars disclosed; rather the disclosure extends to allfunctionally equivalent structures, methods, and uses such as are withinthe scope of the appended claims.

One or more examples or embodiments of the disclosure may be referred toherein, individually and/or collectively, by the term “disclosure”merely for convenience and without intending to voluntarily limit thescope of this application to any particular disclosure or inventiveconcept. Moreover, although specific examples and embodiments have beenillustrated and described herein, it should be appreciated that anysubsequent arrangement designed to achieve the same or similar purposemay be substituted for the specific examples or embodiments shown. Thisdisclosure may be intended to cover any and all subsequent adaptationsor variations of various examples and embodiments. Combinations of theabove examples and embodiments, and other examples and embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the description.

In addition, in the foregoing Detailed Description, various features maybe grouped together or described in a single embodiment for the purposeof streamlining the disclosure. This disclosure may be not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter may bedirected to less than all of the features of any of the disclosedembodiments. Thus, the following claims are incorporated into theDetailed Description, with each claim standing on its own as definingseparately claimed subject matter.

The above disclosed subject matter shall be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure may bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

What is claimed is:
 1. A light emitting device comprising: a lightemitting element having a light emission peak wavelength within a rangeof 430 nm or more and 470 nm or less, and a fluorescent member, whereinthe light emitting device emitting light has a correlated colortemperature in a range of 3,500 K or more and 4,500 K or less, and thefluorescent member comprises: a first fluorescent material that has acomposition shown by the following formula (1), a second fluorescentmaterial that has a composition shown by the following formula (2), athird fluorescent material that has a composition shown by the followingformula (3), and a fourth fluorescent material that has a compositionshown by the following formula (4), wherein the first fluorescentmaterial has a content ratio in a range of 16.5% by mass or more and50.0% by mass or less based on a total fluorescent material amount, thesecond fluorescent material has a content ratio in a range of 28.0% bymass or more and 33.0% by mass or less based on the total fluorescentmaterial amount, the third fluorescent material has a content ratio in arange of 20.0% by mass or more and 35.0% by mass or less based on thetotal fluorescent material amount, and the fourth fluorescent materialhas a content ratio in a range of 3.0% by mass or more and 3.2% by massor less based on the total fluorescent material amount,Sr₄Al₁₄O₂₅:Eu  (1)(x-s)MgO.(s/2)Sc₂O₃ .yMgF₂ .uCaF₂.(1−t)GeO₂.(t/2)M₂O₃ :zMn⁴⁺  (2)wherein in the formula (2), M represents at least one element selectedfrom the group consisting of Al, Ga, and In, and x, y, z, s, t, and urespectively satisfy 2≤x≤4, 0<y<1.5, 0<z<0.05, 0≤s<0.5, 0<t<0.5, and0≤u<1.5,Y₃Al₅O₁₂:Ce  (3)(Sr,Ca)AlSiN₃:Eu  (4).
 2. The light emitting device according to claim1, wherein a content ratio of the first fluorescent material to thethird fluorescent material is in a range of 0.05 or more and 3.00 orless.
 3. The light emitting device according to claim 1, wherein a lightemission peak intensity ratio of the first fluorescent material based ona light emission peak intensity of the light emitting element is in arange of 0.40 or more and 0.75 or less.
 4. The light emitting deviceaccording to claim 1, wherein the first fluorescent material has thehalf value width of the light emission spectrum in a range of 58 nm ormore and 78 nm or less.
 5. The light emitting device according to claim1, wherein the second fluorescent material has the half value width ofthe light emission spectrum in a range of 45 nm or less.
 6. The lightemitting device according to claim 1, wherein the third fluorescentmaterial has the half value width of the light emission spectrum in arange of 95 nm or more and 115 nm or less.
 7. The light emitting deviceaccording to claim 1, wherein the fourth fluorescent material has thehalf value width of the light emission spectrum in a range of 80 nm ormore and 100 nm or less.
 8. The light emitting device according to claim1, wherein a sum of the special color rendering indices R9, R10, R11,R12, R13, R14 and R15 is larger than
 600. 9. A light emitting devicecomprising: a light emitting element having a light emission peakwavelength within a range of 430 nm or more and 470 nm or less, and afluorescent member, wherein the light emitting device emitting light hasa correlated color temperature in a range of 4,500 K or more and 5,500 Kor less, and the fluorescent member comprises: a first fluorescentmaterial that has a composition shown by the following formula (1), asecond fluorescent material that has a composition shown by thefollowing formula (2), a third fluorescent material that has acomposition shown by the following formula (3), and a fourth fluorescentmaterial that has a composition shown by the following formula (4),wherein the first fluorescent material has a content ratio in a range of7.0% by mass or more and 55.0% by mass or less based on a totalfluorescent material amount, the second fluorescent material has acontent ratio in a range of 22.0% by mass or more and 31.0% by mass orless based on the total fluorescent material amount, the thirdfluorescent material has a content ratio in a range of 20.0% by mass ormore and 55.0% by mass or less based on the total fluorescent materialamount, and the fourth fluorescent material has a content ratio in arange of 2.8% by mass or more and 3.0% by mass or less based on thetotal fluorescent material amount,Sr₄Al₁₄O₂₅:Eu  (1)(x-s)MgO.(s/2)Sc₂O₃ .yMgF₂ .uCaF₂.(1−t)GeO₂.(t/2)M₂O₃ :zMn⁴⁺  (2)wherein in the formula (2), M represents at least one element selectedfrom the group consisting of Al, Ga, and In, and x, y, z, s, t, and urespectively satisfy 2≤x≤4, 0<y<1.5, 0<z<0.05, 0≤s<0.5, 0<t<0.5, and0≤u<1.5,Y₃Al₅O₁₂:Ce  (3)(Sr,Ca)AlSiN₃:Eu  (4).
 10. The light emitting device according to claim9, wherein a content ratio of the first fluorescent material to thethird fluorescent material is in a range of 0.06 or more and 4.70 orless.
 11. The light emitting device according to claim 9, wherein alight emission peak intensity ratio of the first fluorescent materialbased on a light emission peak intensity of the light emitting elementis in a range of 0.34 or more and 0.60 or less.
 12. The light emittingdevice according to claim 9, wherein the first fluorescent material hasthe half value width of the light emission spectrum in a range of 58 nmor more and 78 nm or less.
 13. The light emitting device according toclaim 9, wherein the second fluorescent material has the half valuewidth of the light emission spectrum in a range of 45 nm or less. 14.The light emitting device according to claim 9, wherein the thirdfluorescent material has the half value width of the light emissionspectrum in a range of 95 nm or more and 115 nm or less.
 15. The lightemitting device according to claim 9, wherein the fourth fluorescentmaterial has the half value width of the light emission spectrum in arange of 80 nm or more and 100 nm or less.
 16. The light emitting deviceaccording to claim 9, wherein a sum of the special color renderingindices R9, R10, R11, R12, R13, R14 and R15 is larger than
 570. 17. Alight emitting device comprising: a light emitting element having alight emission peak wavelength within a range of 430 nm or more and 470nm or less, and a fluorescent member, wherein the light emitting deviceemitting light has a correlated color temperature in a range of 5,500 Kor more and 7,000 K or less, and the fluorescent member comprises: afirst fluorescent material that has a composition shown by the followingformula (1), a second fluorescent material that has a composition shownby the following formula (2), a third fluorescent material that has acomposition shown by the following formula (3), and a fourth fluorescentmaterial that has a composition shown by the following formula (4),wherein the first fluorescent material has a content ratio in a range of15.0% by mass or more and 40.0% by mass or less based on a totalfluorescent material amount, the second fluorescent material has acontent ratio in a range of 18.0% by mass or more and 20.0% by mass orless based on the total fluorescent material amount, the thirdfluorescent material has a content ratio in a range of 35.0% by mass ormore and 60.0% by mass or less based on the total fluorescent materialamount, and the fourth fluorescent material has a content ratio in arange of 2.6% by mass or more and 2.7% by mass or less based on thetotal fluorescent material amount,Sr₄Al₁₄O₂₅:Eu  (1)(x-s)MgO.(s/2)Sc₂O₃ .yMgF₂ .uCaF₂.(1−t)GeO₂.(t/2)M₂O₃ :zMn⁴⁺  (2)wherein in the formula (2), M represents at least one element selectedfrom the group consisting of Al, Ga, and In, and x, y, z, s, t, and urespectively satisfy 2≤x≤4, 0<y<1.5, 0<z<0.05, 0≤s<0.5, 0<t<0.5, and0≤u<1.5,Y₃Al₅O₁₂:Ce  (3)(Sr,Ca)AlSiN₃:Eu  (4).
 18. The light emitting device according to claim17, wherein a content ratio of the first fluorescent material to thethird fluorescent material is in a range of 0.10 or more and 2.10 orless.
 19. The light emitting device according to claim 17, wherein alight emission peak intensity ratio of the first fluorescent materialbased on a light emission peak intensity of the light emitting elementis in a range of 0.25 or more and 0.42 or less.
 20. The light emittingdevice according to claim 17, wherein the first fluorescent material hasthe half value width of the light emission spectrum in a range of 58 nmor more and 78 nm or less.
 21. The light emitting device according toclaim 17, wherein the second fluorescent material has the half valuewidth of the light emission spectrum in a range of 45 nm or less. 22.The light emitting device according to claim 17, wherein the thirdfluorescent material has the half value width of the light emissionspectrum in a range of 95 nm or more and 115 nm or less.
 23. The lightemitting device according to claim 17, wherein the fourth fluorescentmaterial has the half value width of the light emission spectrum in arange of 80 nm or more and 100 nm or less.
 24. The light emitting deviceaccording to claim 17, wherein a sum of the special color renderingindices R9, R10, R11, R12, R13, R14 and R15 is larger than 610.